Synthesis of low-density [formula omitted] from high-density [formula omitted] in the presence of [formula omitted] melt under high pressure

Abstract

In general, the high-density state is a preferred state of materials under high pressures. In this study, however, when the LiBO 2–Al 2O 3 system quenched from melts at the cooling rate of 50–60 °C/s under high pressures, low density γ - Al 2O 3 was synthesized from high density α - Al 2O 3, with a 7.1% volume expansion of Al 2O 3. While those samples which are quenched at the same cooling rate under a lower pressure appeared to be glassy. The minimal pressure synthesized the low-density γ - Al 2O 3 or the maximal glass forming pressure was decreased with increasing content of Al 2O 3 below its saturation point in LiBO 2 melt.